Oscillation generator for noisemaking devices



B. E. PHELPS Sept. 5, 1950 OSCILLATIIIONI'GENERATOR` FOR NOISE MAKING DEVICES Filed Feb. 21, 19,45

Patented Sept. 5, i950 fwUN- ITED STAT OSCILLATION GENERATOR FOR NOISEMAKIN G DEVICES Byron E. Phelps, Endicott, Y., assignor to International Business Machines Corporation,

New York, N. Y., aI corporationof New York Application February 21, 19%5, Serial No. 579,068

1 claim. (01.' 250-36) This invention relates to a devicefor making a Vnoise simulating the noise of the engines of an airplane, its `principal use at the present time being in association with military training apparatus,'wherein the actual environment of aerial operations is to be reproduced as closely as possible. It isan object of the invention to provide a device of the kind described whereby the noise "can be varied in volume and also in pitch, to correspond with the variations ofengine noises in flight. "'Other objects of the invention will be pointed out in theiollowing description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best inode, which has been contemplated, of applying that principle.

The single' ligure of the drawing -is a circuit diagramof theapparatus. A 'It has been found desirable to provide a plurality of com-plete sound producing units, so that the full audio eiiects `can be realized, including the beat frequencies of a plurality of engines running at slightly different speeds. The drawing shows two complete sound producing units, one above the other. only the upper one will be described in detail.

The sound producing unit comprises an audiofrequency wave generator composed of a power lunit PU and a series of trigger cir-cuits A, B, C, D in cascade connection, to produce 'a base fre- 2 of the left grid rises to about -2 volts, the left side of the tube will begin to conduct and the right side will be cut off by a negative impulse applied through the condenser 25R to the right grid. When the charge on the condenser 2ER.

`drains off to the point where the right grid reaches a potential of -2 volts, the right side of the tube will start to conduct. The process will continue, with the two tubes becoming conductive alternately, in accordance with the Well-known multi-vibrator principle. The frequency of ,the alternations depends upon the circuit constants. Using a SSN? tube. with condensers 2ER and 25L of .l mfd., resistances ISR and I5L of .04 megohrn, resistances 25H. and 26L of .005 megohm, and rheostats 2'IR and 2'IL of 0-.1 megohm, the frequency can be varied from to 300 cycles/ second.

Since these are identical,

4fluency and second, fourth, and eighth sub-harmonic'frequencies. The basevfrequencyis generated in the trigger circuit A, Which is a conventional multi-Vibrator utilizing a twin triode I0, such as 1a GSNZ. rThe plates of this tube are fed through plate resistors I5R and I5L, a wire IB leading to an intermediate point, for instance 240 volts, on the bleeder resistance I1 of the power unit. The bleeder resistance is connected across the output leads I8, I9 of a conventional transformer, rectifier, and Viilter combination, represented by the box 20. The transformer receives alternating current through Wire 23 from a source 2 I, when switch 22 is closed. The cathodes of tube I0 are fed through a Wire 24 from a lower, point, for instance 9 0 volts, on the bleeder resistance I'I. The left platjof the tube I0 is coupled through a condenser 25B. to the right grid of the tube, while the right plate is coupled through a condenser 25L to the left grid. The grids are also connected through fixed grid resistors 261:?J and ZSL and rheostats 21R, and 2'IL to the cathode lead 24. When the power is turned on by closing switch 22 and a voltage is set up across the bleeder resistance I1, one side of the tube I0, say the right side, will start to conduct. This will drive the left grid below the cut-ofi point, until the charge on the related coupling condenser 25L flows off through the grid resistor 26L and rheostat 2'IL. When the voltage The second stage B, wherein the second subharmonic is generated is a trigger circuit, which is stable in either of two conditions and Which reverses in response to negative impulses. The plates of the tube Il of this stage, which may also be a GSN'Y, are connected through resistors @Brand SUL to the B+ Wire IE; the cathodes are connected to the B- wire 24. The two plates are cross connected to the two grids by resistances 3IR, 3IL, and condensers 32B., 32L. Grid resistances 33H, 33L connect the grid to a bias Wire 34 leading to the grounded negative end of the bleeder resistance Il. Also, a coupling is provided from the right plate of tube I0, through wire 35,y and impulsing condensers 3BR, SGL to the grids of tube II.

. It 'will be observed that the right grid of tube I lis connected to a point 3l of a voltage divider consisting of the resistances SGL, 3IR, and 33R, which may have values .02, .2, and .2 megohm, respectively. The left grid is connected to a point 3'|,on a voltage divider 3BR, 3|L, and 33L. With a total drop across these voltage dividers of 240 voli-s, the grids seek a potential of 114 volts, compared to volts on the catliodes` When the .power is turned on, one side of the tube, say the right side, will become conductive, its plate potential will drop, and the left grid will be biased below the cut-off potential. The circuit is stable in this condition, When the right side of the first tube I0 becomes conductive, a negative impulse is transmitted through the impulsing condensers SSR and SSL to the grids of the tube II, reducing the potential on both. grids and cutting off the right side. The resulting rise of the right plate potential causes the potential of the left. grid to rise more steeply than the potential of the right grid, as the condensers 3ER -and 36L discharge,` with the result that the left side becornes conductive and biases oiT the right side. The iznpulsing condensers 3ER and 36L should have somewhat less than half the capacity of the coupling condensers 32B, and 32L; for instance, the former may be .001 and the latter .00045 mfd.

The following ,positive impulse transmitted.

the effect of the positive impulse on the .rightv grid. However, when the next negative impulse is transmitted through the impulsing condensers, the second stage will be reversed in the same manner aspreviously described. Thus, the ysecond stage will `reverse at one-half the rate of theriirst stage.

Thethird and fourth stages C and D, producir-1g` the" fourth and eighth sub-harmonics, 'respectively,are identical to the second stage B. The gridsofvthe tube I'Zf of the third stage are coupled 'fr-orina point on the plate resistor 30R through a Wire 39 and'impuising condensers 4BR and MIL. The grids yof :the'tube lf3 of the fourth stage are 'similarlyscoupled to a point 4l on the plate resister o'fthe right hand section of the third istage;througha wired-3 and impulsing condensers 4'4R'tand ML. The third stage 4.reverses at half the -rateiof the second stage 'and the fourth stage reverseshalf the rate of the third stage, thus producing, respectively, fourth and eighth subharmonics. A resistance 45 and condenser 46 are inserted between the rst and second stages lAnand Bifordecoupling them.

The output 4 of :all four stages is fed int-o a conventionakaudio-frequency amplifier, shown below the audio-.frequency -wa.ve generator. From a oentertapl of the plate resistor IRthe output-,of .the first stage is led through a wire 5I, resistance 52, condenser -53, and volume control 54, tovtheqgrid of-fa-pre-.amplier tube 55, which may .behalf of a-6SN7. The output from each of theother stages. is taken from avolurne control AB through a 4resistance 49 and wire 50 to condenser 53. .The resistance of the Volume controls 4B may be,.5 megohm and that of the resistances .49 and 52 may be 1.0 megohm, while the condenser 53 may be .10 mfd. The plate supply of the tube 55 comes through a plate resistor5a` and a wire 5l from a tap on the bleeder resistance 1],.say 330 volts. The cathode is connecte'dthroughv a grid bias resistance 58 and bypass condenser 5S to ground.

' 'The'pllate of tube 55 is coupled by a condenser '60 and grid resistor 6l to the left grid of the invertertube 62. is vconnected between the left grid and ground. The-left plate of tube 62 is coupled to the conltrol Igrid of the lower output tube 64 by a con- 'denser 66 and grid resistance 61, BB. The right 'grid of tube-E2 is connected to point 69 and its voltageis therefore proportional to the voltage -at the grid of tube 64. The right plate of tube 52 is coupled by condenser I0 and grid resistance '11,158 to the Acontrol grid of the upper output tube G5. The resistances Il, 61 and 68 may be .4, and .1. megohm, respectively. This circuit, known as the floating paraphase causes the 'control grid voltages o the tubes S4 and 65 to vary in exact inverse ratio. The plates of the output tubes are connected to opposite ends of the lprimary coil of an output transformer 12, the center tap of which is connected by a wire 13 v'to the positiveend of the bleeder resistance, hav- 1ing-a potential of 400 volts. The cathodes are 'connected"through a biasing resistor 14 and by- A tone control condenser 63 4 pass y,condenser 'l5 to grolmd.. .JIhe transformer 'l2 serves to couple the aniplierlfto iareceiving device, such as to loud speakers 16. The voice lcoils of these loud speakers are connected in series, lthrough a switch l1, to the secondary .winding'of the transformer 12.

.The steep front waves generated by the four stages of the audio-frequency wave generator cause the loud speakers to produce a sound resembling the noise of an airplane engine. The noise can be simulated more and more closely by proper proportioning of the amplitude of the sub-harmonics by means of the volume controls 48. vIts total volumecan-'be varied A-bv means'of the volume control 54 andits-ipitch by means of the rheostats 2l-L and 21R, for reproducing the 4sound of-an engine in divingand--climbing The secondsound'fgenerator show-nbelow operates loud-speakers '118, the combined output ofthe four loud speakers yielding beat frequencies similar to those generated by=two airplaneV engines.

While there have lbeen shown and `described and pointed out the fundamental-novel features of .the invention xas-applied to a single Amod-idcation, it will be understood that various omissions and substitutions and: changes in. the form and details of the 4cie-vice illustrated Aand its operation may be made vby those skilled in the art without departing'froxn -the spirit of .the invention. It is the intention Ytherefore A.to be limited only `as--indicated bythe scopeof thefollowing claims.

What is claimed is: l

In a device of the class described, anelectronic circuit comprising an oscillator Acircuitand a plurality oftrigger circuits, each having two conditions of stability, said oscillatorcircuit including means to .Vary `the frequency thereof through a wide range, means connecting .said'oscillator and .trigger circuits in cascade .arrangement whereby said oscillator circuit drives an adjacent trigger circuit alternately 4to its two different conditions of stability, so 4thatit reversesat half thefrequency of the oscillator, and whereby each trigger circuit, except the last in .thecascade drives a succeeding trigger circuitalternately to its two diiferentconditions of stability,.so that eachsucceeding-trigger reverses at half the frequency of its driving trigger, a utilization circuit comprising .a single input conductor, and means coupling saidconductor to output points in each of said oscillator and ltrigger circuits so that the outputs of said latter circuits are combined .to form a complex wave in said utilization circuits.

BYRON E. PHELPS.

REFERENCES CITED The'following references are of record in-,the file ofthis patent:

UNITED STATES PATENTS Einmiber Name Date 1,994,902 Trouant Mar. 19, 1935 2,103,450 De Varter Dec. 28, 1937 2,200,618 De Varter May 14, 1940 2,233,258 Hammond et al. Feb. 25, 1941 2,354,699 Owens Aug. 1, 194A 12,404,047 Flory July 16, .1946 .2,410,156 Flory Oct. 29,"1946 2,410,883 Larson et al Nov. 12, 1946 OTHER REFERENCES Review of Scientific Instruments, vol. 14, January 1943,'page 23. (Copy in library.) 

